The thermodynamic study of Na2SO4 and K2SO4 binary and ternary aqueous solutions is materialized in obtaining both average ionic activity coefficients and excess Gibbs energies, from cryometric data. Differential cryometric method utilized for obtaining experimental data has permitted the measurement of cryometric effect with a precision of +/-2 x 10(-4) K. The experimental data process has been obtained using a specific calculation program.